Differences between IMAP, POP3 and SMTP

IMAP or POP3 are used to receive email and SMTP is used to send email.

IMAP	POP3
Mail is stored on the mail server, a copy of email is downloaded locally and accessible offline after full email download.	Downloads email locally, with NO copy on server; accessible offline.
Since email are on server, its accessible from everywhere	Once email is downloaded locally, its can not access from another system/machine normally. (However, some workaround are use to read email on multiple machines, like "Keep email on server for 10 days" setting in Outlook)
Email backup are there on server	Email lost if hard drive failed or if there is no backup

Note: IMAP is better than POP3.


SMTP is use to send email.